Inner rotor motor
By using weak magnetic materials and slip ring brushes in the inner rotor motor, the spark and NVH problems caused by brush friction are solved, while the cost is reduced, achieving a balance between performance and cost, and is suitable for small motors.
Patent Information
- Application Number
- CN202290000893.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-11
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2032-07-11
AI Technical Summary
Existing inner rotor motors have problems such as sparks, NVH and EMC caused by friction between the brushes and the commutator. In addition, brushless motors are expensive, making it difficult to strike a balance between performance and cost.
The stator magnets and slip rings made of weak magnetic materials are electrically connected to the brushes to avoid mechanical commutation. Combined with the electronic commutator, a multi-phase coil and carbon brush design is used to form a stable magnetic field and current conduction.
It reduces motor costs, improves NVH and EMC issues, has performance comparable to brushless motors, and costs close to brushed motors. It has a simple structure and is suitable for small motors.
Smart Images
Figure CN223402370U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of motor technology, and in particular to an inner rotor motor. Background Art
[0002] The motor consists of a stator and a rotor that rotate relative to each other. According to the position relationship between the stator and the rotor, it can be divided into two categories: inner rotor motor and outer rotor motor. Among them, the inner rotor motor has characteristics such as high speed and is widely used in our daily life and industrial production.
[0003] Based on the current commutation method, inner rotor motors can be divided into brushed and brushless motors. Brushed motors use mechanical commutation, offering fast starting, timely braking, and simple control circuits. However, friction between the brushes and the commutator can easily lead to sparks, which not only shortens the brush lifespan but also causes a range of issues, including NVH (Noise, Vibration, Harshness) and EMC (Electromagnetic Compatibility). Brushless motors use electronic commutation, offering advantages such as high efficiency, low noise, and long lifespan. However, their inner rotor size is limited, and achieving the same output torque as a brushed motor of the same size requires the use of magnets made of strong magnetic materials, such as neodymium iron boron, which significantly increases the motor's cost. Utility Model Content
[0004] In view of this, an inner rotor motor is provided that takes into account both motor performance and motor cost.
[0005] An inner rotor motor comprises a stator assembly and a rotor assembly rotatably disposed within the stator assembly, the stator assembly comprising a stator housing, magnets disposed on the inner wall surface of the stator housing, and brushes, the magnets forming a magnetic field stationary relative to the stator housing; the rotor assembly comprising an iron core, a rotating shaft inserted into the iron core, and a coil wound around the iron core; a slip ring is sleeved on the rotating shaft, the slip ring being electrically connected to the coil; one end of the brush abuts the slip ring and the other end is used for electrically connecting to an external AC power supply, the slip ring comprising at least two mutually insulated conductive rings, and the brush comprising at least two mutually insulated carbon brushes, wherein each of the carbon brushes abuts one of the conductive rings, and the at least two conductive rings are arranged at intervals along the radial direction of the rotating shaft.
[0006] In some embodiments, the axis of the magnetic field formed when the coil is energized is relatively stationary with respect to the axis of the magnetic field formed by the magnet.
[0007] In some embodiments, the coil is a multi-phase coil, and the number of the conductive rings is not less than the number of phases of the multi-phase coil, wherein each phase coil is electrically connected to one of the conductive rings.
[0008] In some embodiments, the coil is a single-phase coil, the number of the conductive ring and the number of the carbon brushes are both two, and the two conductive rings are respectively connected to the head and tail ends of the coil.
[0009] In some embodiments, the magnets are electromagnets or permanent magnets and are arranged at intervals along the circumference of the stator housing.
[0010] In some embodiments, the brush is disposed on an end cover, the end cover blocks the axial side end of the stator housing, and a bearing is disposed in the center of the end cover to support the rotation of the rotor assembly.
[0011] In some embodiments, a cap is provided at the other axial side end of the stator housing, and another bearing is provided at the center of the cap to support the rotation of the rotor assembly.
[0012] In some embodiments, a connection terminal electrically connected to the other end of the brush protrudes from the outer side of the end cover, and the connection terminal is used to connect to an external AC power supply.
[0013] Compared with the existing technology, the inner rotor motor of the present application is provided with magnets on its outer stator assembly. The magnets can be made of low-cost weak magnetic materials, which can effectively reduce the cost of the motor. In addition, the slip ring and the brush are only electrically connected and there is no commutation function, which avoids the electric sparks generated by mechanical commutation and improves the NVH, EMC and other problems caused by it. The inner rotor motor of the present application can match the performance of the existing brushless motor and be on par with the cost of the existing brushed motor. In addition, the overall structure is simple and easy to manufacture, and it has broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 This is a schematic structural diagram of an embodiment of an inner rotor motor of the present application.
[0015] Figure 2 for Figure 1 Exploded view of an inner rotor motor shown.
[0016] Figure 3 for Figure 2 Another angle view of the inner rotor motor shown.
[0017] Figure 4 for Figure 1 An axial cross-section of an inner rotor motor is shown.
[0018] Figure 5 This is a schematic diagram of the circuit of the coil of the inner rotor motor of this application.
[0019] Description of Figure Numbers:
[0020] Stator assembly 10, stator housing 12, magnet 14, brush 16, carbon brush 161, end cover 18, connection terminal 181, cap 19;
[0021] The rotor assembly 30 , the iron core 32 , the rotating shaft 34 , the coil 36 , the winding groove 37 , the slip ring 38 , the conductive ring 381 , and the bearing 39 . DETAILED DESCRIPTION
[0022] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings provide exemplary embodiments of the present application to provide a more accurate and thorough understanding of the technical solutions disclosed herein. However, it should be understood that the present application can be implemented in a variety of different forms and is not limited to the embodiments described below.
[0023] The same or similar numbers in the drawings of this application correspond to the same or similar parts; in the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. This is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.
[0024] The present application provides an inner rotor motor, Figure 1-3 A specific embodiment of the present application is shown. The inner rotor motor shown includes a stator assembly 10 and a rotor assembly 30 rotatably disposed in the stator assembly 10 .
[0025] Please also see Figure 3 and Figure 4 The stator assembly 10 includes a stator housing 12 and a plurality of magnets 14 attached to the inner wall surface of the stator housing 12. The magnets 14 are evenly spaced along the circumferential direction of the stator housing 12. Adjacent magnets 14 have opposite polarities. That is, if one of two adjacent magnets 14 has an N pole at its radial inner end and an S pole at its radial outer end, the other has an S pole at its radial inner end and an N pole at its radial outer end. This allows the stator assembly 10 to form alternating N and S poles in the circumferential direction, forming a stator magnetic field that is stationary relative to the stator housing 12. The magnets 14 are located on the outside of the motor and are preferably permanent magnets made of weak magnetic materials such as ferrite. Ferrite materials are mainly composed of iron oxide and other iron or rare earth oxides, and have the advantages of low eddy current loss and low cost.
[0026] It should be understood that, without considering the cost, the magnet 14 can also be a permanent magnet made of a strong magnetic material such as neodymium iron boron; or, the magnet 14 can also be an electromagnet that generates a stable magnetic field when powered.
[0027] Please also see Figure 2 and Figure 3 The rotor assembly 30 includes an iron core 32, a rotating shaft 34 inserted into the iron core 32, and a coil 36 wound on the iron core 32. The iron core 32 can be made of a plurality of stacked silicon steel sheets, including a yoke portion that is sleeved with the rotating shaft 34 and a plurality of teeth extending radially outward from the yoke portion. The rotating shaft 34 is fixedly inserted into the yoke portion of the iron core 32, and its two ends extend outside the iron core 32 to transmit power outward. The coil 36 is wound on each tooth portion, and adjacent teeth are spaced apart in the circumferential direction to form a winding slot 37 for winding the coil 36. The coil 36 preferably adopts a three-phase coil (U, V, W), and each phase coil 36 can be composed of multiple coils connected in parallel or in series. Figure 5 In the figure, different phases of the coils 36 are shown with different line types, such as the U-phase coil shown by the dotted line, the V-phase coil shown by the dotted line, and the W-phase coil shown by the solid line.
[0028] like Figure 2 As shown, the rotor assembly 30 further includes a slip ring 38 sleeved on the rotating shaft 34, and the stator assembly 10 further includes a brush 16 provided corresponding to the slip ring 38, and the brush 16 abuts against the slip ring 38. When the inner rotor motor rotates, the slip ring 38 rotates coaxially with the rotating shaft 34. During the rotation process, the brush 16 always abuts against the slip ring 38 to cooperate with the slip ring 38 so that an external power supply can power the coil 36.
[0029] The slip ring 38 includes at least two mutually insulated conductive rings 381, and the brush 16 includes at least two mutually insulated carbon brushes 161, each carbon brush 161 abutting against one of the conductive rings 381. The at least two conductive rings 381 can be arranged along the axial direction of the rotating shaft 34, for example Figures 2 to 4As shown, the at least two carbon brushes 161 are arranged axially with spacing, forming a height difference in the axial direction of the motor. The inner end of each carbon brush 161 abuts against the radial outer wall of one of the conductive rings 381 and is electrically conductive. The at least two carbon brushes 161 can be arranged in an axially aligned manner or staggered in the axial direction. The diameters of the at least two conductive rings 381 can be the same or different. In some embodiments, the at least two conductive rings 381 can also be arranged radially along the rotating shaft 34, such as at least two concentric rings spaced apart in the radial direction. Correspondingly, the brush 16 can be aligned with the slip ring 38 in the axial direction, such as being arranged on the axial side of the slip ring 38 facing away from or toward the iron core 32. Each carbon brush 161 abuts against the end face of one of the conductive rings 181 and is electrically conductive. The at least two carbon brushes 161 can be arranged in a radially aligned manner or staggered in the radial direction.
[0030] It should also be noted that the slip ring 38 can be mounted on any suitable position on the rotating shaft 34. Positioning the brushes 16 and slip ring 38 on the same side of the motor facilitates electrical connection to an external power source. In some embodiments, the conductive rings 381 of the slip ring 38 can also be positioned at either end of the rotating shaft 34, and correspondingly, the carbon brushes 161 of the brush 16 can also be positioned at either end of the motor. This application does not specifically limit the arrangement and position of the at least two conductive rings 381 and the at least two carbon brushes 161. All arrangements that insulate the conductive rings 381 from each other, insulate the carbon brushes 161 from each other, and ensure electrical continuity between each carbon brush 161 and a conductive ring 381 are within the scope of this application.
[0031] In the embodiment of the present application, the magnetic field axis formed by the coil 36 when energized is relatively stationary with respect to the magnetic field axis formed by the magnet 14. Preferably, a commutation circuit is connected in series between the coil 36 and the external power supply. The commutation circuit controls the phase of the current in the coil 36 to maintain the stator and rotor magnetic field axes relatively stationary. The commutation circuit can be integrated into a control circuit board within the motor; alternatively, the commutation circuit can serve as an external control circuit for the motor.
[0032] The coil 36 is a multi-phase coil or a single-phase coil. Accordingly, the external power source is an AC power source, such as a multi-phase or single-phase AC power source. When the coil 36 is a multi-phase coil, the number of conductive rings 381 is no less than the number of phases of the multi-phase coil. Each phase coil 36 is electrically connected to one of the conductive rings 381. Thus, each phase coil 36 can be electrically connected to the external power source via a conductive ring 381 and a carbon brush 161 abutting the conductive ring 381. The number of conductive rings 381 is preferably equal to the number of phases of the multi-phase coil. When the coil 36 is a single-phase coil, the number of conductive rings 381 and the number of carbon brushes 161 are both two. The two conductive rings 381 are respectively connected to the head and tail ends of the single-phase coil. Thus, both ends of the head of the single-phase coil can be electrically connected to the external power source via a conductive ring 381 and a carbon brush 161 abutting the conductive ring 381.
[0033] In some embodiments, the brushes 16 are fixedly mounted on the inside of an end cap 18, which is secured to an axial side of the stator housing 12. At least two connection terminals 181 protrude from the outside of the end cap 18, electrically connected to the outer ends of the at least two carbon brushes 161. These at least two connection terminals 181 are used to connect to an external AC power source. Preferably, the other axial side of the stator housing 12 is capped with a cap 19. The cap 19 and the center of the end cap 18 each have bearing seats for mounting bearings 39. The ends of the rotating shaft 34 are respectively inserted into a bearing 39, which supports the rotating shaft 34, enabling stable rotation of the rotor assembly 30.
[0034] The following describes the inner rotor motor of the present application using a three-phase coil as an example. Figures 2 to 4 As shown, the slip ring 38 used has three conductive rings 381, and the brush 16 has three carbon brushes 161. When the inner rotor motor of the present application is started, three-phase AC power is transmitted to the three-phase coils 36 of the rotor assembly 30 through the cooperation of the three carbon brushes 161 and the three slip rings 381. The AC power can be a sine wave, a square wave, etc. The current in each phase coil 36 forms a phase difference of 120 degrees, thereby generating a rotating magnetic field, allowing the rotor assembly 30 to continuously rotate relative to the stator assembly 10. During the rotation of the rotor assembly 30, the carbon brushes 161 and the conductive rings 381 always maintain electrical conductivity, serving as an electrical connection. It should be understood that the coils 36 of the rotor assembly 30 can be configured with any number of phases, such as four or five phases. In this case, the number of conductive rings 381 and carbon brushes 161 is adjusted according to the number of phases of the coils 36. Each conductive ring 381 connects one phase of the coil 36 to the external power supply. The present embodiment only uses a three-phase coil as an example, but is not limited to this.
[0035] The inner rotor motor of this application uses slip rings 38 and brushes 16 to supply AC power to coils 36. The rotor assembly 30 is located in the center of the motor and includes an excitation coil 36. The stator assembly 10 is located outside the motor and includes magnets 14. The overall structure is similar to that of existing brushed DC motors. Because magnets 14 are located closer to the outside of the motor, they can be larger and made of weakly magnetic materials. This significantly reduces motor costs compared to existing brushless motors, which must use strong magnetic materials for their rotors. Coil 36 is wound around the core 32 of rotor assembly 30 using the fly winding method used in existing brushed motors. This is simpler and faster than the needle winding and segmented winding methods used in existing brushless motors, further reducing motor costs.
[0036] In the present application, the slip ring 38 and the brush 16 cooperate to conduct current without the need for current commutation. Compared with existing brushed motors, the generation of electric sparks can be effectively avoided, the service life of the brush 16 can be increased, and EMC can be improved. In addition, the bounce generated when the brush 16 is separated from the commutator in the existing brushed motor can also be avoided, and the NVH and other problems caused by this can be reduced. In addition, the present application sets an electronic commutator instead of mechanical commutation, which can effectively reduce torque pulses and further reduce NVH. In short, the inner rotor motor of the present application is comparable to the existing brushless motor in performance and is on par with the existing brushed motor in cost. It can effectively balance motor performance and motor cost, and is particularly suitable for small motors, such as the 48V motor used in electric vehicles.
[0037] It should be noted that the present application is not limited to the above-mentioned embodiments. Based on the creative spirit of the present application, those skilled in the art may also make other changes. These changes made based on the creative spirit of the present application should be included in the scope of protection required by the present application.
Claims
1. An inner rotor motor, comprising a stator assembly and a rotor assembly rotatably disposed within the stator assembly, characterized in that: The stator assembly includes a stator shell, a magnet arranged on the inner wall surface of the stator shell, and a brush, wherein the magnet forms a magnetic field that is stationary relative to the stator shell; the rotor assembly includes an iron core, a rotating shaft inserted into the iron core, and a coil wound around the iron core; a slip ring is sleeved on the rotating shaft, and the slip ring is electrically connected to the coil; one end of the brush abuts the slip ring, and the other end is used to be electrically connected to an external AC power supply.
2. The inner rotor motor according to claim 1, wherein: The axis of the magnetic field formed when the coil is energized is relatively stationary with respect to the axis of the magnetic field formed by the magnet.
3. The inner rotor motor according to claim 1, wherein: The slip ring includes at least two conductive rings insulated from each other, and the brush includes at least two carbon brushes insulated from each other, wherein each of the carbon brushes abuts against one of the conductive rings.
4. The inner rotor motor according to claim 3, wherein: The coil is a multi-phase coil, and the number of the conductive rings is not less than the number of phases of the multi-phase coil, wherein each phase coil is electrically connected to one of the conductive rings.
5. The inner rotor motor according to claim 3, wherein: The coil is a single-phase coil, and the number of the conductive ring and the number of the carbon brushes are both two, and the two conductive rings are respectively connected to the head and tail ends of the coil.
6. The inner rotor motor according to claim 3, wherein: The at least two conductive rings are arranged at intervals along the axial direction of the rotating shaft, or the at least two conductive rings are arranged at intervals along the radial direction of the rotating shaft.
7. The inner rotor motor according to any one of claims 1 to 6, characterized in that: The magnets are electromagnets or permanent magnets and are arranged at intervals along the circumference of the stator housing.
8. The inner rotor motor according to any one of claims 1 to 6, characterized in that: The brush is arranged on the end cover, and the end cover blocks the axial side end of the stator shell. A bearing is arranged in the center of the end cover to support the rotation of the rotor assembly.
9. The inner rotor motor according to claim 8, wherein: A cap is provided at the other axial side end of the stator housing, and another bearing is provided at the center of the cap to support the rotation of the rotor assembly.
10. The inner rotor motor according to claim 8, wherein: A connecting terminal electrically connected to the other end of the brush protrudes from the outer side of the end cover, and the connecting terminal is used to connect to an external AC power supply.